This invention relates to polyester compositions, their method of manufacture, and uses of the compositions, for example as optical reflectors in lighting applications.
Molded items comprising thermoplastic resins have been used for optical reflectors that can be used for automotive headlight extensions and reflectors, for indoor illumination, for vehicle interior illumination and for the like, with vapor deposited films of metal having been formed on the surfaces of said molded items.
Polyester resin is often used for such molded items because of its high thermal and flow properties. However, because the surfaces of the molded items do not ordinarily possess satisfactory gloss or there is roughness in the surfaces, they are treated with primer as an undercoat before vapor deposition of the reflective surface. Such primer treatment adds a processing cost, so improvements are sought so that vapor deposition can be performed directly on the molded item. For this reason, it is necessary to develop resin compositions that can be molded into molded items that have high gloss, and whose metallized (e.g., vapor deposited metal) surfaces do not subsequently become clouded by generated gases, even when heated.
It is thought that direct deposition processing that does not use primers will become the mainstream for the purposes of simplifying manufacturing processes, in addition to economics, and environmental problems. Several polyester resin compositions have been proposed that allow direct vapor deposition.
For example, Japan Unexamined Patent Publication H11-241006 discloses light reflectors with metal directly deposited on molded items made from polyester resin compositions that have modified silicon oil, organophosphorus compound, fine powder filler and organic nucleating agent blended into mixed resin comprising polyalkylene terephthalate resin and polycarbonate resin.
Also, Japan Unexamined Patent Publication 2000-212294 discloses automotive parts made from blending layered silicates, in which organic ions have replaced exchangeable cations present between the layers, into thermoplastic polyester. Japan Unexamined Patent Publication 2001-316573 discloses lamp parts made from compositions comprising an epoxy group-containing substance and reinforcing agent in thermoplastic polyester.
Japan Unexamined Patent Publication 2002-179895 discloses compositions for optically reflecting molded items that have polyalkylene naphthalate in polybutylene terephthalate. Also, Japan Unexamined Patent Publication 2000-35509 discloses a method for manufacturing a reflector comprising molding a resin composition that has polyethylene terephthalate resin and a non fibrous inorganic filler having an average grain size equal to or less than 10 micrometers (μm) into polybutylene terephthalate resin that has less that 50 milliequivalents per kilogram (meq/kg) terminal carboxyl groups, and directly forming optically reflecting metal layer on at least a portion of the molded article. Furthermore, Japan Unexamined Patent Publication 2002-294042 discloses an optical reflector that has an optically reflecting metal layer formed on at least a portion of a molded article made from a composition having lanthanum oxide blended into polyester resin.
However, articles with satisfactory molding characteristics, metal layer adhesion, gloss, etc. cannot be obtained from the compositions disclosed in the above References to. There are four characteristics required for direct vapor deposition of metal layers.                1) Mold shrinkage during moldingIf mold shrinkage is high, dimensional stability of the molded article and release from the mold become problems.        2) Good gloss of the surface of the molded item and the absence of adhesion patterns that arise from adhesion to the moldIt is necessary that the resin has satisfactory release properties and contains nothing that would cause a loss of gloss.        3) Absence of adhered matter on the molds after lengthy molding timesBecause out gassing from the resin composition deposit/sticks to the mold surface and these adhere to the surfaces of the molded articles, the molds must be cleaned every few hours.        4) Absence of cloudiness, rainbow patterns, etc. in the vapor deposited surface even after heating the vapor deposited surface of the molded item.The conventional technologies published in the above patent References have difficulty in obtaining items that satisfy all four of these characteristics.        
This applicant proposed in Japan Unexamined Patent Publication H11-293099, as a composition for reflectors in automotive headlights, resin compositions for direct vapor deposition that contain polyarylate resin and polyester resin that has aliphatic diol residues.
Furthermore, this applicant proposed in Japan Unexamined Patent Publication 2003-261750 polyester resin compositions that possess certain heat distortion temperatures and contain (a) thermoplastic polyester, (b) inorganic filler, (c) 0 to about 400 parts by weight of at least one kind of polycarbonate, and (d) an antistat agent, and the use of these resin compositions for optical reflectors. However, for the compositions disclosed in this reference, undercoating is necessary when they are used for optical reflectors.
There accordingly remains a need in the art for polyester molding composition that have low shrinkage, low residuals on the surface of the article or mold after demolding, good gloss, and good gloss retention after exposure to heat. It would be a further advantage if the compositions could be used in the manufacture of articles having an excellent appearance after metallization without a separate undercoating step.